EP0541431B1 - Méthode et dispositif pour restituer un signal d'horloge rythmant la transmission de signaux reçus - Google Patents
Méthode et dispositif pour restituer un signal d'horloge rythmant la transmission de signaux reçus Download PDFInfo
- Publication number
- EP0541431B1 EP0541431B1 EP92402964A EP92402964A EP0541431B1 EP 0541431 B1 EP0541431 B1 EP 0541431B1 EP 92402964 A EP92402964 A EP 92402964A EP 92402964 A EP92402964 A EP 92402964A EP 0541431 B1 EP0541431 B1 EP 0541431B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- frequency
- shifts
- signal
- signals
- local clock
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 230000005540 biological transmission Effects 0.000 title claims description 33
- 238000000034 method Methods 0.000 title claims description 16
- 230000007704 transition Effects 0.000 claims description 24
- 238000012937 correction Methods 0.000 claims description 23
- 238000005070 sampling Methods 0.000 claims description 20
- 230000010354 integration Effects 0.000 claims 1
- 238000001514 detection method Methods 0.000 description 3
- 230000006870 function Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000033764 rhythmic process Effects 0.000 description 2
- 230000009118 appropriate response Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000009633 clock regulation Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
- H04L7/0334—Processing of samples having at least three levels, e.g. soft decisions
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
Definitions
- the present invention relates to a method and a device to restore from signals received on a transmission channel any clock signal that punctuates the transmission on this digital and coded data channel.
- the invention can be used in bipolar coded transmission such as HDB3 code but it finds its full justification in simultaneous transmission systems of several pieces of information such as multi-level transmission.
- the digital data to be transmitted is coded on the basis of a defined number of different electrical voltages of constant amplitude. For example, 4, 8, 16 or 32 symmetrical coding voltages are chosen two by two on either side of the 0 volt voltage. Thus, with 2 n , it is possible to transmit n bits simultaneously and thus increase the transmission rate of a transmission channel.
- a transmission application on a cable using multi-level coding is described for example in French patent application EN 91/05375.
- a known method for restoring a clock signal punctuating a coded transmission consists in applying the signals coded to a frequency and phase servo loop.
- the received signal is mixed for example with a signal generated by a local oscillator controlled by an electrical voltage (VCO) (or a derived signal), and the low frequency component extracted from the signal handset is applied to a local oscillator control input which locks on the frequency of the received signal (or on a proportional frequency) after a more or less long setting time according to the initial difference.
- VCO electrical voltage
- the clock signal timing the transmission being restored by this setting of the loop it is possible to precisely position a window for measuring the voltage level electric received between two successive transitions of coded signals received.
- patent EP-A-198 701 we know a device analog phase comparator. It detects phase differences between that of an input signal punctuated by a clock signal and a reference clock. It includes a converter analog-digital which samples the signal received at the frequency of the local clock signal and produces digital words of K bits, and a delay circuit which samples the same signal received at twice the frequency of the clock signal. A multiplication of the digital words obtained in both cases (by a or-exclusive). produces data representative of the phase variations between the input signal and clock signal.
- the object of the process according to the invention is therefore an exact restitution to from signals picked up on a transmission channel, from a period clock signal T punctuating the transmission thereon of digitized and coded data, by a precise detection of successive transition instants of coded signals received in the purpose of phasing a local clock.
- the step of comparing all the deviations with the list of configuration of deviations is carried out by associating for example with each set level deviations obtained, signals indicative of any correction to be made at the frequency or phase of the local clock.
- the method comprises for example a binary coding of the deviations after comparison with a threshold amplitude.
- the device making it possible to restore a clock signal pacing the transmission of captured signals and phasing of a local clock, in agreement with the method, includes means for adapting the level of the signals received on a transmission channel, means for sampling the signals received during time intervals each including at least one transition between levels different from the coded signals received at a frequency imposed by the local clock and very higher than that of the clock signal to have a plurality of samples successive signals received, means for determining the level deviations one with respect to the others of the samples taken during each of said intervals of time and constitute with each of them a set of deviation values, and means to compare each set of level differences with a list of binary words predetermined indicative of the centering quality of the sampled transition, comprising storage means for associating values with each set deviation obtained, signals indicative of the correction to be applied to the local clock to restore synchronization with the clock signal.
- the sampling means are preferably adapted to deliver digital words, said means for determining the differences, comprise two registers adapted to contain successive digital words, means of two-by-two comparison of successive digital words contained in the two registers, and means for memorizing deviations to contain said sets deviations.
- the comparison means are adapted for example to compare each deviation from a threshold deviation.
- storage means comprising a memory for digital words representative of corrections to be applied to the local clock, this memory being provided with inputs connected to the means for memorizing deviations, as well as a local clock comprising an oscillator with high frequency, first frequency dividing means for dividing the frequency of the oscillator signal by several different factors around a central value, and selecting one of the factors as a function of said correction signals (CR o , CR 1 ) received from the decoding means (20), and from the second divider means connected to the first divider means for generating a first signal at the same frequency (f o ) as the received clock signal and a synchronization signal at a frequency (F o ) multiple of that of the first signal.
- the sampling means may include a analog to digital converter.
- the frequency (F o ) of said synchronization signal is chosen for example to obtain a number 2 n of samples during a transition and sampling means suitable for delivering digital words of n bits for each of them are used.
- Signals S 1 or S 2 such as those shown in FIG. 1 are obtained from a certain number of electrical voltages of determined amplitude (eight or sixteen for example).
- Each of its successive stages N1 ... Np corresponds to a particular combination of binary signals which can be transmitted simultaneously on a transmission channel, as is well known to specialists.
- the precise determination of the level of each of the successive stages of the signal received on this channel makes it possible to restore the binary signals transmitted.
- the measurement of each of the levels is carried out during a window W which must be well centered on each of the stages of duration T to avoid any error in the recognition of the level.
- each of the windows is carried out by a local clock and it can only be precise if this clock is perfectly timed on the one which served to rhythm the transmission of signals on the transmission channel. It is therefore necessary to accurately detect the transition times of the signals received even when they are more or less distorted due to imperfections in the transmission channel and the transmission device such as the signal S 2 .
- the method according to the invention firstly comprises sampling of coded signals received during intervals of time D each including at least one level transition of the signals coded received. This sampling can be done at time intervals more or less long. It is, however, advantageous to carry it out preferably each of the successive periods of the signal received for a better accuracy.
- the sampling frequency and duration of the interval D are chosen to obtain a determined number separate samples. In Figs. 2 and 4, we see that the interval sampling time D is centered on a signal period and that 8 samples a1, a2, ..., a8 are successively taken during this interval.
- the method then includes a comparison of the amplitudes respective successive samples taken so as to determine their deviations. If two successive samples have the same level (or amplitude) their deviation is assigned the value 0. When their levels are different, we assign the logical value 1 to their deviation. Every set of samples, so we can associate a binary word of 8 bits. In Figs. 3 and 5, we see that the numerical words obtained are different depending respectively on whether the centering of the interval D by relative to a selected signal portion is correct, and that one is out of sync with each other.
- Each binary word obtained is compared to a list of words predetermined binaries. Each of them corresponds to a configuration determined deviation indicative of the quality of the centering of the sampled transition with respect to the time interval d.
- the positioning of the sampling window by signal relation can be arbitrary. It can be focused on signal transitions for example if we choose to detect moments when they occur or during the signal periods so as to detect the midpoints of successive periods.
- the coded signals coming from the transmission channel used 1 are applied to a low-pass filter 2.
- the weakening of the filtered signals due to the transmission is compensated by an automatic gain control assembly 3 comprising a variable attenuator 4, an amplifier 5 and an envelope detector 6 connected to the output of the amplifier 5, which controls the attenuation factor of the attenuator 4.
- the signals from the assembly 3 are applied to a regulation assembly clock 7 which receives from a local clock 8, clock signals at frequencies multiple from each other, this assembly being used to detect the clock signals rhythm of the received signals, and in return transmit signals of correction D o and D 1 capable of adjusting, if necessary, the frequencies of the local clock 8 to resynchronize it.
- This local clock 8 comprises (FIG. 9) a high frequency oscillator 9 and a division assembly 10 adapted to divide the frequency of the signal of the oscillator 9 by several factors around a central factor. In practice, for example, 3 factors 7, 8 and 9 are chosen, the central factor here being 8.
- the function of this division set 10 is also to select one of the three resulting signals as a function of the correction signals CR 0 or CR 1 .
- the clock regulation assembly 7 comprises (FIG. 9) a comparison means 12 adapted to continuously compare the amplitude of the regulated signals coming from the assembly 3 with 7 thresholds of increasing amplitude for example and delivering in response 3-bit digital words D o , D 1 , D 2 .
- This comparison means 12 advantageously consists of an analog-digital converter.
- the digital words are applied to two registers 13, 14 at successive sampling instants fixed by the clock signal at the clock frequency F o , the two registers 13, 14 are connected in series so that the digital words pass successively in both. These words or consecutive digitized samples are compared to each other at the same frequency by a comparison means 15 adapted to determine their possible deviation.
- the comparator delivers a logical 1 if any two digitized samples have different amplitudes, and a logical 0 otherwise.
- the binary values coming successively from the comparison means 15 are transferred to a shift register 16 to 8 bits.
- the 8-bit words formed are stored in a register 17. Each of these 8-bit words corresponds to a configuration of deviations representative of the signal sampled during the time interval D.
- the next operation which consists in recognizing whether this configuration is acceptable, is performed in an element of memorization 18 of the PROM type.
- each of the digital words applied therefore refers to an address of the memory 18 where a 2-bit digital word CR 0 and CR 1 is stored which will be used to define whether a correction of the frequency of the local clock is necessary and the direction of this possible correction.
- Each 8-bit word from the register 17 represents both a standard configuration and the address of the memory 18 where the appropriate response is written, which must be given according to the configuration obtained.
- the comparison operation is performed automatically by leaving the signals representative of the correction to be made from the memory at the designated address.
- a certain number of them correspond to cases where the synchronism between the frequency of the clock detected on the transmission channel and the local clock is considered to be correct. Others correspond to cases where the local clock is ahead of the transmitted clock signal. Still other standard configurations correspond to cases where the local clock is late.
- the digital words CR 0 , CR 1 from the memory 18 are successively loaded into a register 19 and applied to the division assembly 10.
- the register 19 plays a role of integrator. It applies an average correction calculated over a determined number of successive measurement cycles and therefore makes it possible to avoid so-called "jitter” phenomena.
- the application of the appropriate correction signal CR 0 , C R 1 results in the selection of a higher division factor (8 in l 'occurrence) for the division unit 10, so as to decrease the frequencies f o and F o produced by the dividing elements 11.
- a delay of the local clock on the contrary has the effect of selecting the lower division factor (7 in the example) by the division unit 10 and an increase in the same frequencies.
- the transmission channel on which the coded signals are receipts can be a transmission line. It can also be consisting of a radio channel consisting of a carrier modulated with modulation of a known type suitable for signals to transmit.
- the logical coding of the deviations is carried out by the comparison means 15 without weighting.
- a weighting of deviations the logical value 1 not being assigned to the deviation only if it is greater than a threshold value determined so to eliminate certain unimportant and unimportant level fluctuations impact on the quality of the synchronism detection sought.
- a threshold comparator can be interposed in this case between the comparison means 15 and the register 16 (Fig. 9).
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
Description
- un échantillonnage des signaux codés reçus durant des intervalles de temps incluant chacun au moins une transition entre deux niveaux différents des signaux codés reçus, et à une fréquence suffisante imposée par l'horloge locale et très supérieure à celle du signal d'horloge pour disposer d'un nombre déterminé d'échantillons successifs des signaux reçus;
- une détermination des écarts de niveau entre tous les échantillons successifs obtenus;
- une comparaison de l'ensemble desdits écarts de niveau obtenus au cours de chaque intervalles de temps (D) et une liste de mots binaires prédéterminés, chacun de ces mots binaires correspondant à une configuration-type d'écarts déterminée indicative de la qualité du centrage de la transition échantillonnée par rapport à l'intervalle de temps (D), et si l'ensemble des écarts ne correspond pas à une configuration d'écart de cette liste;
- une correction de la fréquence ou de la phase de l'horloge locale, de façon à rétablir une similitude avec une configuration d'écarts de la liste lors d'une transition ultérieure.
- la Fig.1 montre deux exemples de signaux à niveaux multiples reçus sur une voie de transmission et plus ou moins déformés par la transmission;
- la Fig.2 montre un intervalle de temps d'échantillonnage correctement placé par rapport à une portion particulière de signal reçu, dans le cas où l'horloge locale est bien synchrone avec le signal d'horloge rythmant un signal reçu;
- la Fig.3 montre un mot numérique traduisant les écarts de niveau entre les échantillons prélevés, dans le cas de la Fig.2;
- les Fig. 4 et 5 sont analogues aux Fig. 2 et 3 et elles correspondent au cas où l'intervalle de temps d'échantillonnage est mal centré du fait d'une désynchronisation de l'horloge locale;
- les Fig. 6 et 7 correspondent au cas où l'on choisit une fenêtre d'échantillonnage à cheval sur une transition du signal et le mot numérique correspondant obtenu;
- la Fig.8 montre schématiquement le dispositif selon l'invention; et
- la Fig.9 montre plus en détail le schéma de la Fig.8.
Claims (11)
- Procédé pour restituer à partir de signaux captés sur une voie de transmission, un signal d'horloge (H) rythmant la transmission sur celle-ci de données numérisées et codées, par une détermination des instants de transition successifs où les signaux codés changent de niveaux d'amplitude, de façon à mettre en phase une horloge locale, caractérisé en ce qu'il comporte la réalisation de cycles comprenantun échantillonnage des signaux codés reçus durant des intervalles de temps (D) incluant chacun au moins une transition entre deux niveaux différents des signaux codés reçus et à une fréquence (Fo) suffisante imposée par l'horloge locale (8) et très supérieure à celle dudit signal d'horloge pour disposer d'une pluralité d'échantillons (a1-a8) successifs, des signaux reçus;une détermination des écarts de niveau entre tous les échantillons successifs obtenus;une comparaison de l'ensemble desdits écarts de niveau obtenus au cours de chaque intervalles de temps (D) et une liste de mots binaires prédéterminés, chacun de ces mots binaires correspondant à une configuration-type d'écarts déterminée indicative de la qualité du centrage de la transition échantillonnée par rapport à l'intervalle de temps (D), et si l'ensemble des écarts ne correspond pas à une configuration d'écarts de cette liste;une correction (CR0, CR1) de la fréquence ou de la phase de l'horloge locale, de façon à rétablir une similitude avec une configuration d'écarts de la liste, lors d'une transition ultérieure.
- Procédé selon la revendication 1, caractérisé en ce que ladite étape de comparaison de l'ensemble des écarts avec la liste de configuration d'écarts est effectuée en associant directement à chaque ensemble d'écarts de niveau obtenu, des signaux (CR0, CR1) indicatifs de la correction éventuelle à apporter à la fréquence ou la phase de l'horloge locale.
- Procédé selon la revendication 1 ou 2, caractérisé en ce qu'il comporte un codage binaire des écarts.
- Procédé selon la revendication 1 ou 2, caractérisé en ce qu'il comporte un codage binaire des écarts après comparaison avec une amplitude seuil.
- Dispositif pour restituer un signal d'horloge rythmant la transmission de signaux captés et mettre en phase une horloge locale (8), en accord avec le procédé selon la revendication 1 ou 2, comportant des moyens (2, 3) d'adaptation du niveau des signaux reçus sur une voie de transmission, caractérisé en ce qu'il comporte des moyens (12) d'échantillonnage des signaux reçus durant des intervalles de temps incluant chacun au moins une transition entre des niveaux différents des signaux codés reçus à une fréquence suffisante imposée par l'horloge locale et très supérieure à celle du signal d'horloge, pour disposer d'une pluralité d'échantillons successifs des signaux reçus, des moyens (13-17) pour déterminer les écarts de niveau les uns par rapport aux autres des échantillons successifs prélevés durant chacun desdits intervalles de temps et constituer avec chacun d'eux un ensemble de valeurs d'écart, et des moyens de comparaison de chaque ensemble d'écarts de niveau avec une liste de mots binaires prédéterminés indicative de la qualité de centrage de la transition échantillonnée, comprenant des moyens de mémorisation (18, 19) pour associer à chaque ensemble de valeurs d'écart obtenu, des signaux indicatifs de la correction à appliquer à l'horloge locale pour rétablir la synchronisation avec ledit signal d'horloge.
- Dispositif selon la revendication 5, caractérisé en ce que les moyens d'échantillonnage (12) sont adaptés à délivrer des mots numériques, lesdits moyens (13-17) pour déterminer les écarts, comportent deux registres (13, 14) adaptés à contenir les mots numériques successifs, des moyens (15) de comparaison deux à deux des mots numériques successifs contenus dans les deux registres (13, 14), et des moyens de mémorisation des écarts (16, 17) pour contenir lesdits ensembles d'écarts.
- Dispositif selon la revendication 5, caractérisé en ce que les moyens de comparaison (15) sont adaptés à comparer chaque écart à un écart seuil.
- Dispositif selon la revendication 6, caractérisé en ce que les moyens de mémorisation (18, 19) comportent un organe de mémorisation (18) pour des mots numériques (CR0, CR1) représentatifs de corrections à appliquer à l'horloge locale (8), ledit organe de mémorisation (18) étant pourvu d'entrées d'adresse reliées auxdits moyens de mémorisation des écarts (17), et en ce que l'horloge locale comporte un oscillateur à haute fréquence (9), des premiers moyens diviseurs de fréquence (10) pour diviser la fréquence du signal de l'oscillateur par plusieurs facteurs différents autour d'une valeur centrale, et sélectionner l'un des facteurs en fonction desdits signaux de correction (CR0, CR1) reçu desdits moyens de mémorisation (18, 19) et des deuxièmes moyens diviseurs connectés aux premiers moyens diviseurs pour engendrer un premier signal à la même fréquence (Fo) que le signal d'horloge reçu ainsi qu'un signal de synchronisation à une fréquence (Fo) multiple de celle du premier signal.
- Dispositif selon l'une des revendications 5 à 8, caractérisé en ce que les moyens d'échantillonnage (12) comportent un convertisseur analogique-numérique.
- Dispositif selon la revendication précédente, caractérisé en ce que la Fréquence (Fo) dudit signal de synchronisation est choisie pour obtenir un nombre 2n d'échantillons durant chacun desdits intervalles de temps et les moyens d'échantillonnage (12) sont adaptés à délivrer des mots numériques de n bits pour chacun d'eux.
- Dispositif selon la revendication 8, caractérisé en ce que lesdits moyens de mémorisation comportent des moyens d'intégration (19) pour l'application d'une correction moyenne établie sur un nombre déterminé de cycles successifs.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9113770 | 1991-11-06 | ||
FR9113770A FR2683411B1 (fr) | 1991-11-06 | 1991-11-06 | Methode et dispositif pour restituer un signal d'horloge rythmant la transmission de signaux recus. |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0541431A1 EP0541431A1 (fr) | 1993-05-12 |
EP0541431B1 true EP0541431B1 (fr) | 1998-07-22 |
Family
ID=9418735
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP92402964A Expired - Lifetime EP0541431B1 (fr) | 1991-11-06 | 1992-10-30 | Méthode et dispositif pour restituer un signal d'horloge rythmant la transmission de signaux reçus |
Country Status (6)
Country | Link |
---|---|
US (1) | US5566215A (fr) |
EP (1) | EP0541431B1 (fr) |
CA (1) | CA2082288C (fr) |
DE (1) | DE69226331T2 (fr) |
FR (1) | FR2683411B1 (fr) |
NO (1) | NO305340B1 (fr) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2728409B1 (fr) * | 1994-12-16 | 1997-03-14 | Sgs Thomson Microelectronics | Circuit de restitution de bits transmis de maniere asynchrone |
FR2730884B1 (fr) * | 1995-02-17 | 1997-04-04 | Inst Francais Du Petrole | Methode et dispositif pour regenerer, par detection des maxima, un signal d'horloge rythmant la transmission de signaux numerises recus |
NO307858B1 (no) * | 1998-05-25 | 2000-06-05 | Ericsson Telefon Ab L M | FremgangsmÕte relatert til klokkeforsinkelseskompensasjon |
US7636642B2 (en) * | 2003-06-19 | 2009-12-22 | Teradyne, Inc. | Direct jitter analysis of binary sampled data |
JP2006119723A (ja) * | 2004-10-19 | 2006-05-11 | Canon Inc | 画像処理装置、画像処理方法 |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3746800A (en) * | 1971-08-16 | 1973-07-17 | Rixon | Clock recovery system |
US4031478A (en) * | 1976-06-29 | 1977-06-21 | International Telephone And Telegraph Corporation | Digital phase/frequency comparator |
JPH0624291B2 (ja) * | 1985-04-17 | 1994-03-30 | 日本電気株式会社 | 位相検出回路 |
JPH01144738A (ja) * | 1987-11-30 | 1989-06-07 | Nec Home Electron Ltd | ウインドウ法同期保護回路 |
US5208833A (en) * | 1991-04-08 | 1993-05-04 | Motorola, Inc. | Multi-level symbol synchronizer |
US5297172A (en) * | 1991-04-11 | 1994-03-22 | Comsat Corporation | Method and apparatus for clock recovery for digitally implemented modem |
US5245637A (en) * | 1991-12-30 | 1993-09-14 | International Business Machines Corporation | Phase and frequency adjustable digital phase lock logic system |
-
1991
- 1991-11-06 FR FR9113770A patent/FR2683411B1/fr not_active Expired - Lifetime
-
1992
- 1992-10-30 DE DE69226331T patent/DE69226331T2/de not_active Expired - Fee Related
- 1992-10-30 EP EP92402964A patent/EP0541431B1/fr not_active Expired - Lifetime
- 1992-11-04 NO NO924247A patent/NO305340B1/no not_active IP Right Cessation
- 1992-11-06 US US07/972,814 patent/US5566215A/en not_active Expired - Lifetime
- 1992-11-06 CA CA002082288A patent/CA2082288C/fr not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
NO924247L (no) | 1993-05-07 |
CA2082288A1 (fr) | 1993-05-07 |
CA2082288C (fr) | 2007-07-03 |
FR2683411B1 (fr) | 1994-12-09 |
NO924247D0 (no) | 1992-11-04 |
DE69226331T2 (de) | 1998-12-03 |
EP0541431A1 (fr) | 1993-05-12 |
FR2683411A1 (fr) | 1993-05-07 |
NO305340B1 (no) | 1999-05-10 |
US5566215A (en) | 1996-10-15 |
DE69226331D1 (de) | 1998-08-27 |
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